Multi-layered pneumatically supported structures

ABSTRACT

Embodiments of the present disclosure relate to a structure that comprises at least one layer of air beams that define an interior space of the structure wherein laterally adjacent air beams are configured to laterally abut each other. Optionally the structure comprises at least a first layer of a plurality of air beams and a second layer of a second plurality of air beams, wherein the second layer is positioned adjacent to and interior to the first layer for defining an interior space of the protective structure. A structure with laterally abutting air beams may better protect the occupants and contents within the structure from the effects of an explosion. Constructing a structure with at least two layers of air beams may provide a stiffer structure as compared to a structure that is constructed from a single layer of air beams.

TECHNICAL FIELD

The present disclosure generally relates to protective structures. Inparticular the present disclosure relates to protective structures thatcomprises one or two layers with each layer comprising a plurality ofinflatable air beams that are configured to be laterally abutting andwhere the two layers form at least an inner layer and an outer layer ofthe structure.

BACKGROUND

Explosive events generate blast waves that are often the cause ofsignificant injury to people. The types of human injuries that typicallyoccur due to explosions may be divided into three categories: (i)primary injuries that result directly from blast overpressure andshock-wave effects; (ii) secondary injuries that result from impactswith airborne fragments, debris, structural deformations and the like;and (iii) tertiary injuries resulting from the people being physicallypropelled by the blast wave. Blast waves can also be transmitted fromoutside a structure to inside the structure as a shock wave, which canalso cause injuries to the structure's occupants.

It is known to construct protective structures from a layer of air beamsthat are covered with a polymer sheet-material, which is referred to asa fly. These protective structures are designed to protect occupantsfrom the effects of explosive blast-loads. The protective structures areinherently resistant to blast loading as a direct consequence of theflexible properties of the air beams and the fly. These flexibleproperties allow a significant but controlled flexure in the event ofsevere blast-loads where deformation of the protective structure absorbsaspects of the blast loads, which ultimately minimizes injury risk tooccupants or damage to any material housed within the protectivestructure.

For example, protective structures that are made with a layer of airbeams can reduce the potential for primary, secondary, and tertiaryinjuries to occupants. The potential for primary and tertiary injuriesis reduced by partial mitigation of blast-pulse transmission to theinterior of the structure. The possibility of secondary injury is alsoreduced in comparison to a rigid building that may lose structuralintegrity and have surfaces fragment or tear away, which can createfurther hazards.

However, the desirable flexible properties of the air beams may alsolimit the ability to make pneumatically-supported protective structuresbeyond a given size, which may limit the applications of such protectivestructures. Furthermore, even the flexible properties of the air beamsdoes allow some transmission of a shock wave into the interior of theprotective structures.

SUMMARY

Embodiments of the present disclosure relate to a structure thatcomprises at least one layer of air beams that define an interior spaceof the structure wherein laterally adjacent air beams are configured toabut each other.

Some embodiments of the present disclosure relate to a structure thatcomprises at least a first layer of a plurality of air beams and asecond layer of a second plurality of air beams, wherein the secondlayer is positioned adjacent and interior to the first layer fordefining an interior space of the structure.

Inflated structures are comprised of inflated air beams that are made upof fabric the inflation pressure, tube radius, and material stresses areconnected through the relationship:

S=pr

where:

-   -   S is the fabric hoop stress (in units of Force/Distance vs.        Engineering Stress in units Force/[(distance){circumflex over        ( )}2];    -   p=tube inflation pressure; and    -   r=tube radius.

So that for air beams that are inflated at a constant pressure, thestress in the material increases proportionally with radius (likewise,for tubes of constant radius, stress increases proportional topressure). As the clear span of the structure increases, the air beamdiameter (and therefore radius) must be increased to withstand theadditional loads especially snow loads and wind loads. As the radiusincreases, with constant inflation pressure, the stress in the fabricmembrane containing the air pressure also increases. Eventually, as thespan of a structure is increased, the stress in the fabric due toinflation pressure only, not due to other loading becomes unacceptablyhigh. This may be due to one or more several concurrent constraints:

-   -   Due to a complex response of textile fabric under load, the        Factor of Safety (FoS) is commonly set quite high typically        between 5 and 7 for fabric as compared to about 2 for structural        steel. The stress-strain characteristics of fabrics are both        nonlinear, and characterized by several discrete loading        regimes, in each of which the average modulus of elasticity is        significantly different. Therefore, in an effort to avoid        troublesome loading regions, the FoS is usually set high.    -   The seam strength for heat-fused coated fabrics is lower than        the strength of the base material (unlike for steel where the        welded connection is typically stronger than the steel) as the        fabric stresses increase, the risk of (longitudinal) seam        failure increases.    -   As the radius of a tube increases, the weight of the air beams        increases (due to more fabric being used).    -   Increasing fabric stress can be compensated for with heavier        fabric, but this also increases weight of the air beams.

At some point, the designer can no longer continue increasing thediameter of the air beams. Without being bound by any particular theory,as the size of the intended structure increases using two or more layersof air beams may be suitable alternative to larger diameter air beamswhen one or more constraints prevent increasing the diameter anyfurther. This is primarily due to the fact that the primary constrainton using two or more layers of air beams is that it requires twice thematerial of an equivalent single-layer structure.

Constructing a protective structure with at least two layers of airbeams may provide a stiffer structure as compared to a structure that isconstructed from a single layer of air beams. A stiffer structure can bebuilt to larger dimensions with larger interior spaces. These interiorspaces may be sufficiently large to enclose an already constructedbuilding or structure. Furthermore, when the protective structures haveat least two layers of air beams and the air beams within each layer arelaterally abutting each other, the protective structure can defeat thetransmission of a shock wave through the at least two layers. Defeatingthe transmission of a shock wave may reduce the primary, secondary andtertiary injuries that can occur when a shock wave is transmitted insidea structure.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features of the present disclosure will become moreapparent in the following detailed description in which reference ismade to the appended drawings.

FIG. 1 is an isometric view of one embodiment of the present disclosurethat relates to a structure;

FIG. 2 is a series of different views of the structure shown in FIG. 1:FIG. 2A is a front elevation, midline, cross-sectional view of thestructure shown in FIG. 1; FIG. 2B is a top plan view of a section ofthe structure shown in FIG. 2A; FIG. 2C is a bottom plan view of thesection shown in FIG. 2B; and FIG. 2D is a side-elevation view of thesection shown in FIG. 2B;

FIG. 3 is a schematic illustration of embodiments of the presentdisclosure that relate to various configurations of air beams: FIG. 3Ashows a first configuration; FIG. 3B shows a second configuration; FIG.3C shows a third configuration; and FIG. 3D shows a fourthconfiguration;

FIG. 4 is a schematic illustration of embodiments of the presentdisclosure that relate to various further configurations of air beams:FIG. 4A shows the first configuration; FIG. 4B shows the secondconfiguration; FIG. 4C shows a variation of the second configuration;FIG. 4D shows another variation of the second configuration; FIG. 4Eshows a variation of the fourth configuration; FIG. 4F shows anothervariation of the second configuration; FIG. 4G shows another variationof the fourth configuration; and FIG. 4H shows another variation of thesecond configuration;

FIG. 5 shows an example of a shock-tube assembly and exampleconfigurations of target samples tested therein: FIG. 5A is a sideelevation, midline schematic of a shock-tube assembly that was used foracquiring data from a target sample; and FIG. 5B is a top plan schematicof the example configurations of air beams and flys that were used astarget samples within the shock-tube assembly;

FIG. 6 is a line graph that shows an example of overpressure vs. timedata that was captured within a shock-tube assembly without a targetsample;

FIG. 7 is a line graph that shows an example of overpressure vs. timedata that was acquired at a second sensor and a third sensor within theshock-tube assembly when a test-sample was present;

FIG. 8 is a line graph that shows an example of overpressure vs. timedata that was acquired at a second sensor and a third sensor within theshock-tube assembly when a different test-sample was present;

FIG. 9 is a line graph that shows an example of overpressure vs. timedata that was acquired at a second sensor and a third sensor within theshock-tube assembly when a different test-sample was present;

FIG. 10 is a line graph that shows an example of overpressure vs. timedata that was acquired at a second sensor and a third sensor within theshock-tube assembly when a different test-sample was present;

FIG. 11 is a line graph that shows an example of overpressure vs. timedata that was acquired at a second sensor and a third sensor within theshock-tube assembly when a different test-sample was present;

FIG. 12 is a line graph that shows an example of overpressure vs. timedata that was acquired at a second sensor and a third sensor within theshock-tube assembly when a different test-specimen was present;

FIG. 13 is a line graph that shows an example of overpressure vs. timedata that was acquired at a second sensor and a third sensor within theshock-tube assembly when a different test-specimen was present;

FIG. 14 is a bar graph that compares the peak overpressure data from thedata provided in FIG. 6 through to FIG. 13;

FIG. 15 is an isometric view of a schematic of one example of a shearcontrol system according to embodiments of the present disclosure;

FIG. 16 is an isometric view of a schematic of another example of ashear control system according to embodiments of the present disclosure;

FIG. 17 is an isometric view of a schematic of another example of ashear control system according to embodiments of the present disclosure;

FIG. 18 is an isometric view of a schematic of another example of ashear control system according to embodiments of the present disclosure;

FIG. 19 is a dot plot that shows an example of experimental data thatcompares the collapse load (“breakpoint”) of air beams in bending, usingvarious shear control systems;

FIG. 20 is a combined side elevation view and isometric view of aschematic of an example of a connection system according to embodimentsof the present disclosure;

FIG. 21 is a top plan view of two parts of the connection system shownin FIG. 20;

FIG. 22 is a top plan view of the connection system shown in FIG. 20;and

FIG. 23 is a top plan view of the connection system shown in FIG. 20 foruse with multiple air beams in two layers.

DETAILED DESCRIPTION

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this disclosure belongs.

As used herein, the term “about” refers to an approximately +/−10%variation from a given value. It is to be understood that such avariation is always included in any given value provided herein, whetheror not it is specifically referred to.

Embodiments of the present disclosure relate to a structure that can berapidly deployed proximal a site of interest. The structure may at leastpartially protect the site of interest from an explosion. Alternatively,or complimentarily, the structure may be large enough to provide a largeinterior space with various commercial uses, industrial uses,recreational uses and combinations thereof. The structure comprisesmultiple air beams that may also be referred to as fabric beams,pneumatic beams, pneumatic columns, pneumatic arches or pneumatictubulars. The air beams may be arranged in one or more configurations toform ribs of the structure with multiple ribs forming a frame of thestructure. A fly that is made of a sheet material may be incorporatedinto or on top of the ribs to enclose the frame. Connection systems mayalso be employed to connect the air beams to each other to form thestructure and optionally to incorporate the fly. The configuration ofthe air beams determines the type of protection the structure providesto the site of interest and the overall size that the structure can be.

Embodiments of the present disclosure relate to a structure that is madeup of at least two layers of air beams. Each layer comprises a pluralityof air beams that substantially abut a laterally adjacent air beam sothat a plurality of abutting air beams within a layer form part of orall of a wall of the structure. One layer of air beams forms an innerlayer and one layer of air beams forms an outer layer. Some embodimentsof the present disclosure relate to structures with more than two layersof air beams that comprise an inner layer, an outer layer and one ormore intermediate layers therebetween.

Embodiments of the present disclosure will now be described by referenceto FIG. 1 to FIG. 14.

FIG. 1 shows one example of a structure 10. The structure 10 may includeone or more doors 200 to provide access to an interior space 12 of thestructure 10 (shown in FIG. 2A). While FIG. 1 shows a specificarrangement of four doors 200, this is provided merely as anillustrative example and it is not intended to be limiting. For clarity,the structure 10 is shown in FIG. 1 without a fly 218, which isdiscussed further herein below.

FIG. 2A shows a midline cross-section of the structure 10 that is takenperpendicular to the longitudinal axis of the structure 10 (thedirection of the longitudinal axis is shown as line X in FIG. 1). Thestructure 10 comprises as least a first layer 10A and a second layer10B. Each layer 10A, 10B comprises one or more air beams 14, with airbeams 14A forming the first layer 10A and air beams 14B forming thesecond layer 10B. The air beams 14 are made of a fluid tight material sothat a desired volume and pressure of an inflating fluid, such as air orother mixtures of gases, can be contained within each air beam 14.

As shown in the non-limiting depiction of the structure 10 in FIG. 2A,one or more air beams 14 may extend from one side of the structure 10 tothe other side to form a rib 15, which may also be referred to as anarch. Multiple ribs 15 are arranged in an abutting relationship to forma frame of the structure 10 in the shape of a barrel vault.Alternatively, multiple air beams 14, of successively smaller span, maybe connected with each other to enclose the open ends of the barrelvault portion of the structure 10 in a manner similar to that shown inthe region of rib 15. In some embodiments of the present disclosure, afirst portion (shown as X₂ in FIG. 2A) of the structure 10 may bedefined by one or more air beams 14 that extend away from the groundupon which the structure 10 is deployed. In some embodiments of thepresent disclosure the structure 10 may be constructed without a firstportion X₂. In some embodiments of the present disclosure the structure10 may be tethered to the ground by various approaches, including atethermast and/or a frag wall, as described in the Applicant's patentapplication WO 2011072374 entitled Tethermast and Frag Wall, the entiredisclosure of which is incorporated herein by reference. In someembodiments of the present disclosure, the rib 15 includes the firstportion X₂. In some embodiments of the present disclosure, the ribs 15are dimensioned to provide a total span (shown as Y₁ in FIG. 2B) ofabout 200 meters. In some embodiments of the present disclosure, theribs 15 are dimensioned to provide a span that is selected from a groupof about 175 meters, about 150 meters, about 125 meters, about 100meters or less. In some embodiments of the present disclosure the ribs15 are dimensioned to provide a span that is between about 35 meters toabout 125 meters. In some embodiments the total span may be smaller orlarger than the range provided above. The peak height (shown as X₁ inFIG. 2A) of the structure 10 may fall between a range of 2 and 100meters. In some embodiments the peak height may be smaller or largerthan the range provided above.

In some embodiments of the present disclosure, the structure 10 maydefine a large enough interior space 12 so that another building orstructure will fit therein. In this fashion, the structure 10 could bedeployed about an existing building, either as a temporaryprotective-structure or as a longer-term protective structure or forproviding a large enough interior space 12 so that various commercial,industrial and/or recreation activities can occur therein. As describedfurther below, when the structure 10 is constructed with at least twolayers 10A, 10B, the ribs 15 are sufficiently stiff enough to supportthe large spans. Furthermore, the at least two layers 10A, 10B providefurther protection from blast waves and transmitted pressure waves whencompared to when similar structures are constructed of a single layer ofair beams and subjected to similar blast waves.

The air beams 14 within and among the layers 10A, 10B may be similar toeach other, or not. In some embodiments of the present disclosure theair beams 14A, 14B can be filled with a fluid, such as air, to a rangeof desired pressures. An air beam 14 may have a diameter between about0.01 meters and about 2.5 meters or other broader ranges.

Within the embodiments of the present disclosure that are shown in FIG.2B and FIG. 2C, there are three air beams 14A with each air beam in anabutting relationship with a laterally adjacent air beam 14A of thefirst layer 10A. While in an abutting relationship with a laterallyadjacent air beam, there is substantially no gap between the adjacentair beams. In this abutting relationship, the laterally-adjacent airbeams may be direct contact with each other and they may be physicallycoupled together by a connection system, or not. In other embodiments ofthe present disclosure there may be a gap so that there is no contactbetween laterally-adjacent air beams when the air beams are static. FIG.2A shows the first layer 10A as an outer layer and the second layer 10Bas being an inner layer, which may also be referred to as an interiorlayer. The second layer 10B may define the dimensions of the interiorspace 12.

FIG. 3 shows a cross-sectional, top plan view of a number of differentconfigurations of air beams 14 that may be useful in making the ribs 15of the structure 10. The structure 10 may comprise ribs 15 of the sameconfiguration or the ribs 15 may be of different configurations. FIG. 3Ashows a first configuration with a single air beam 14 with a diameter ofabout 0.8 meters. FIG. 3B shows a second configuration of air beams witha first layer 10A that includes two air beams 14A and a second layer 10Bwith two air beams 14B, the air beams 14 in the second configurationhave a diameter of about 0.4 meters. FIG. 3C shows a third configurationof air beams with a first layer 10A with a single air beam 14A and asecond layer 10B with a single air beam 14B. The air beams 14 in thethird configuration have a diameter of about 0.8 meters. FIG. 3D shows afourth configuration of air beams that includes a first layer 10A, asecond layer 10B and an intermediate layer 10C, each layer in theconfiguration has a single air beam with a diameter of about 0.8 meters.Within the second, third and fourth configurations, the air beams 14A ofthe first layer 10A are substantially aligned centrally with the airbeams 10B of the second layer 10B. As used herein, the expression“aligned centrally” refers to the relative position of an air beam inone layer compared to one or more air beams in another layer. Thealigned centrally means that the center point of an air beam of onelayers is aligned with the center point of an air beam in another layerso that if a straight line was drawn that extends from the center pointof one of the air beams being referred to—where the line extendssubstantially orthogonal to the respective layer of the air beam beingreferred to—that line may also extend through the center point of an airbeam in another layer (see line Z1 in FIG. 4B).

FIG. 4 shows a top plan view of a number of different configurations ofair beams 14 that also may be useful in making ribs 15 of the structure10. FIG. 4A shows the first configuration of FIG. 3A. FIG. 4B shows thesecond configuration with a first layer 10A and a second layer 10B,wherein the air beams 14A of the first layer 10A are substantiallyaligned with the air beams 10B of the second layer 10B.

FIG. 4C shows a fifth configuration of air beams 14 with a single airbeam 14A from the first layer 10A for every two air beams 14B of thesecond layer 10B with the air beam 14A aligned offset and in between thetwo air beams 14B. As used herein, the expression “aligned offset”refers to a central point of an air beam in one layer being offsetrelative to the central point in an air beam in an immediately adjacentlayer. If a straight line was drawn that extends from the center pointof one of the air beams being referred to—where the line extendssubstantially orthogonal to the respective layer of the air beam beingreferred to—that line will not extend through the center point of an airbeam in the immediately adjacent layer (see line Z2 in FIG. 4C). Ratherthat line will extend through a lateral edge region of an air beam inthe immediately adjacent layer. In some embodiments of the presentdisclosure, when air beam 14A (in layer 10A) is of equal diameter to airbeams 14B (in layer 10B) (as shown in FIGS. 4C and 4D) a line be drawnto connect the centers of these three air beams and this line willdefine an equilateral triangle.

FIG. 4D shows a sixth configuration with a single air beam 14B from thesecond layer 10B for every two air beams 14A of the first layer 10A. Thesingle air beam 14B is aligned approximately in between the two airbeams 14A of the first layer 10A.

FIG. 4E shows a seventh configuration with an intermediate layer 10Cthat is made up of a single air beam 14C that is positioned in themiddle of and aligned approximately in between the two air beams 14A ofthe first layer 10A and two air beams 14B of the second layer 10B.

FIG. 4F shows an eighth configuration with two air beams 14A of thefirst layer 10A is aligned approximately in between and three air beams14B of the second layer 10B.

FIG. 4G shows a ninth configuration that includes a single air beam 14Aof the first layer 10A, two air beams 14C of the intermediate layer 10Cand three air beams 14B of the second layer 10B. The air beams 14 inthis ninth configuration are all aligned approximately in between theair beams of an adjacent layer.

FIG. 4H shows an tenth configuration that includes three air beams 14Aof the first layer 10A that are each aligned approximately in betweenthree air beams 14B of the second layer 10B.

While the description of these air beam configurations include specificdimensions of air beams 14, it is understood that these diameters areexamples only and the embodiments of the present disclosure are notlimited to these specific dimensions.

Some embodiments of the present disclosure include connection systemsfor connecting air beams 14 within a configuration of two or more layers10 of air beams 14. Some embodiments of the present disclosure relate toconnection systems that act as shear control systems for controlling orreducing shear forces between air beams 14A in one layer and air beams14B in an adjacent layer.

FIG. 15 shows a shear control system 1 that comprises at least one setof a strap 100 and a pocket 102. The pocket 102 can be secured to theouter surface of one air beam 14A in the first layer 10A and the strap100 can be wrapped around both air beams 14A and 14B and through thepocket 102. The pockets 102 can be secured by the use of suitableadhesives and/or attachment techniques such as sonic welding, thermalpolymer-welding and the like. In some embodiments of the presentdisclosure the strap 100 can be a webbing ratchet strap and the pocket102 can be made of a vinyl fabric. There can be multiple sets of straps100 and pockets 102 along the length of the air beams 14A, 14B. As willbe appreciated by one skilled in the art, the layer 10A, 10B in whichthe pocket 102 is secured can be the same or different between differentsets of straps 100 and pockets 102 that are distributed along the lengthof the air beams 14A, 14B. Furthermore, each set of the shear controlsystem 1 may include more than one strap 100 and more than one pocket102. For example, there may be a pocket 102 secured to an air beam 14 ineach layer 10, or not. While FIG. 15 shows two layers, it is understoodthat the shear control system 1 may be used in configurations that havemore than two layers.

FIG. 16 shows a shear control system 2 that comprises one or more setsof a first hug strap 104, a second hug strap 106 and a length of webbing108. The first hug strap 104 is secured about the outer surface of oneair beam 14A and the second hug strap 106 is secure about the outersurface of an air beam 14B in an adjacent layer 10. Each hug strap 104,106 may have a loop extension (not shown) that is positioned in thecontact area between the two air beams 14A and 14B. The hug straps 104,106 can be positioned in an offset manner (as shown in FIG. 16) so thatthe loop extensions are positioned proximal each other so that the hugstraps 104, 106 are configured for receiving a portion of the length ofwebbing 108 therethrough for connecting the air beam 14A to air beam14B. As will be appreciated by one skilled in the art, in configurationsthat have more than two layers 10, the hug straps 104, 106 may each havemore than one extension loop positioned at each contacting surfacebetween the layers 10 of the configuration.

FIG. 17 shows a shear control system 4 that comprises one or more setsof a pair of fixed point connectors 109 and bracing straps 110. In thisshear control system, each of the fixed point connections 109 can beloop or circular members, such as O rings or D rings, and one of thepair of fixed point connections is secured to the outer surface of airbeam 14A and the other fix point connection of the pair is secure to theouter surface of air beam 14B. The bracing straps 110 are connected atopposite ends to the fixed point connection 109 that make up a pair. Thebracing straps 110 can have an adjustable length so that when they areshortened a tension load acts on the fixed point connections 109 torestrict or prevent movement of air beam 14A relative to air beam 14B.As shown in the non-limiting example of FIG. 18, the fixed pointconnection 109 can be positioned so that the bracing straps 110 areoriented in a pattern of alternating direction. As will be appreciatedby one skilled in the art, the number of fixed point connection 109 andbracing straps 110 utilized in this example of the shear control systemcan be variable based upon the length of the air beams 14 used and thenumber of layers 10 in a given configuration.

FIG. 18 shows a shear control system 5 that is similar to the systemshown in FIG. 17. The primary difference in the system of FIG. 18 isthat there are only two sets of fixed point connections 109 and bracingstraps 110 and each set is positioned near an end of the air beams 14Aand 14B.

Not shown in the drawings is a shear control system (Ctrl) thatcomprises paired strips of hook and loop portions of a hook and loopfastener that are secured to the outer surface of two air beams 14 andeach portion extends along the entire axial length of each air beam andeach portion is positioned within the contacting area so that when thetwo air beams 14 are brought close enough together the hook and loopportions connect to form the hook and loop fastener.

FIG. 20 shows a shear control system 3 that is similar to the system(Ctrl) but the paired strips of a hook portion 120A and a loop portion120B are not continuous along the entire axial length of air beams.Rather the portions 120A and 120B are smaller lengths that do not extendthe entire axial length of the air beams 14. Each air beam 14 may havemultiple pairs of laterally displaced hook portions 120A or loopportions 120B that are positioned along the length of the air beam 14.

FIG. 19 shows examples of experimental data obtained from four-pointbending experiments where air beams with 65 cm diameters were connectedinto a two layer configuration using each of the shear control systems 1through 5. The bending experiments were conducted with the air beamsinflated to a low pressure (1 psi) and a high pressure (2 psi). As shownin FIG. 19 the system (Ctrl) and system 3 had the highest breakpointresults (with minimal differences between the two hook and loop fastenerbased systems), which is an indication of the ability of these systemsto restrict movement of the air beams of one layer relative to anotherlayer.

FIG. 20 also shows an example of a connection system that includes theshear control system 3 and a lateral connection system that comprisesstraps 122 and 126 that each extend laterally from an air beam 14A inlayer 10A. Strap 122 can include a first portion 124A of a fastener 124,such as a hook portion 124A of a hook and loop fastener 124 and strap126 can include a second portion 124B of the fastener, such as anassociated loop portion 124B of the hook and loop fastener 124. Theperson skilled in the art will appreciate that there is no requirementthat the fastener 124 is a hook and loop fastener 124, rather the firstportion 124A merely needs to be mateable with the second portion 124B toform a completed (fastened) fastener 124. Further examples of thefastener 124 include buckles, press fit fasteners and the like. Air beam14A also includes non-continuous hook portion 120A that are positionedaxially along the length of air beam 14A. Air beam 14B has loop portions120B that are positioned axially along the length of the air beam 14Band positioned to mate with the hook portions 120A of air beam 14A. FIG.21 also shows the components of the connection system on each of airbeam 14A and air beam 14B. The person skilled in the art will appreciatethat FIG. 21 is not limiting and the hook portions 120A, 124A and thestraps 122 and 126 can be part of air beam 14B and the loop portions120B, 124B can be part of the air beam 14B.

FIG. 22 shows how the hook portion 120A can be positioned proximal tothe loop portion 120B to mate and form a complete (fastened) hook andloop fastener 120 (as shown within the hash lined circle of FIG. 22).FIG. 22 also shows one example arrangement whereby the strap 122 of oneair beam 14A can be positioned around an outer portion of air beam 14Band the strap 126 can also be positioned around the outer portion of airbean 14B so that hook portion 124A can mate with loop portion 124B tomake a complete (fastened) hook and loop fastener 124 (as shown withinthe hash lined circle in FIG. 22). As one skilled in the art willappreciate, the drawings show the straps 122 and 126 as extending fromair beams 14A and the air beam 14B as including the fasteners 120B butthis is but one example that may provide easier access to the straps 122and 126 for mating the fasteners to make the completed hook and loopfasteners 124. In some embodiments of the present disclosure, the straps122 and 126 may extend laterally from the air beam 14B and the air beam14A may include fastener portion 120B.

FIG. 23 shows one example of the connection system used to interconnectmultiple air beams 14A of one layer with air beams 14B of another layerby using the portions of the hook and loop fasteners 120, 124 describedherein above to restrict or reduce shear between layers of air beams andto provide a configuration with any gap between laterally adjacent airbeams of one layer.

While FIG. 23 shows a configuration where the layers are aligned offset,the person skilled in the art will appreciate that the positioning ofthe hook portions 120A, 124A and the loop portions 120B, 124B can beadjusted so that the air beams of the two (or more) layers are alignedcentrally. Without being bound by any particular theory, when air beamsin two or more adjacent layers are aligned centrally, there can beincreases in the structural strength of the structure, which means thatlarger spans can be contemplated. In contrast, when air beams in two ormore adjacent layers are aligned offset and the air beams within eachlayer are laterally abutting, there may be improved blast-relatedproperties (e.g. a further attenuation of any transmitted pressurethrough the layers of air beams) and this may be because the respectiveair beams are in a somewhat nested position relative to each other.

EXAMPLES Example 1: Material-Property Analysis

The inventors performed an initial analysis that illustrates the benefitof a multilayer configuration of air beams 14. This analysis was basedon comparing the first configuration (FIG. 3A) and the secondconfiguration (FIG. 3B). This is a useful comparison, because it allowsa comparison of stiffness and load-bearing properties on the basis ofthe same width, depth, and area of wall section (as shown by the dottedsquares shown in FIG. 3A and FIG. 3B).

A complication arises, however, in the case of inflated fabricstructures such as air beams. For conventional engineering materials,the material properties are not dependent on the arrangement; for fabricstructures, the effective material properties are highly dependent onprestress loading (among other parameters), and there is a tightrelationship between prestress loading, inflation pressure, and tubediameter. In order to compare the first and second configurations on anequitable basis, the air beams of the second configuration must beinflated at precisely twice the pressure as the air beam in the firstconfiguration. This is referred to as the “constant prestress” (versus“constant pressure”) condition.

Table 1 provides theoretical stiffness properties and predicted spanlength of the first, second, third and fourth configurations of airbeams.

TABLE 1 Theoretical stiffness and span values for four configurations ofair beams. Configuration Type

First Second Third Fourth Configuration Configuration ConfigurationConfiguration Stiffness 100% 75% 300% 633% relative to (constant FirstConfiguration pressure) 150% (constant prestress) Low estimate 100% n/a173% 252% High estimate 100% n/a 200% 300%

Testing focused on four-point flexural tests to determine the overallstructural response of an air beam within each of the first, second,third and fourth configurations to a bending load, and to determine anappropriate value for the modulus of elasticity, E (also known asYoung's Modulus).

Briefly, the four-point flexural tests were performed as follows:

Load was applied continuously using a winch system with the loadmeasured by a load cell and the displacement was measured by a draw-wiresensor attached to the bottom of the air-beam configuration beingtested. The load and displacement data were recorded using a computerdata-acquisition system.

Load was applied to the air-beam configuration being tested through two30 cm (12″) wide load straps that were draped over the air-beamconfiguration and attached to an aluminum frame hanging below theconfiguration. The straps were located at about ⅓ of the span of theair-beam configuration for the majority of the tests. For this series oftests the span between the supports was about 4.65 m (load strap spacing1.55 m for ⅓ span loading). A number of tests were also performed withthe straps near the center of the configuration (strap spacing 66 cm(26″)).

The air-beam configurations were supported by yokes that matched thecurvature of the air beams within the configurations to minimize anydeformation of the air beams at the supports. The yokes were hinged andset on casters to allow for rotation and horizontal displacement as theconfiguration bent under the influence of the load.

-   -   Table 2 summarizes experimental results from four-point bending        tests on single layers of air beams and on double layers of air        beams to assess structural properties of the air beam layers.

TABLE 2 A summary of experimental results from four-point bending testsperformed on single layers of air beams with diameters of 50 cm, 65 cmand 80 cm and on double layers of air beams with each layer having airbeams with diameters of 50 cm or 65 cm. Data Source k F_(c)Configuration (Study No.) (N/mm) (N) Single-Layer 50 cm ø 2 6.47 624.0665 cm ø 3 11.78 1439.97 80 cm ø 1, 2 17.30 2742.93 Dual-Layer 100 cmS.D. 4A, 4B 16.87 2274.29 (2 × 50 cm ø) 130 cm S.D. 4B 29.39 4060.07 (2× 65 cm ø)

In Table 2, Fc represents the mean collapse load of each configurationof air beams. The dual-layer configurations tested both showsubstantially higher Fc values as compared to the single-layers made upof air beams with the single layers.

Applying the empirical result factor of 93% to actual span data, andassuming a maximum practical span of a structure that is constructedwith ribs 15 of the first configuration is about 33.5 meters (about 110feet), this provides low and high estimates for the maximum predictedspan of dual-layer and triple-layer structures, as shown in Table 3below.

TABLE 3 A summary of calculated span lengths for the first, third andfourth configuration of air beams. Configuration Type

First Third Fourth Configuration Configuration Configuration Maximum Low33.5 m (110′) 56.0 m (184′)  81.4 m (267′) predicted span High 67.1 m(220′) 100.6 m (330′)

Example 2: Blast-Tube Testing

A blast tube 200 is a type of shock tube, an example of which is shownin FIG. 5A. Briefly, the blast tube 200 comprises a driver section 202in which an explosive event 204 is triggered. The pressure wave, whichmay also be referred to as a blast wave, shock wave or a blast pulse,generated by the explosive event 204 travels through a transitionsection 206 and into a driven section 208. The driven section 208includes an upstream wall-mounted pressure sensor 210 and a frontpressure-sensor 212. Adjacent the front pressure-sensor 212 ispositioned a test sample 216 that may include a fly 218. Behind the testsample is a rear pressure-sensor 214. The pressure sensors 212, 214 weredisc-type pressure sensors. During these experiments, the frontpressure-sensor 212 was positioned about 0.5 meters (about 20 inches)away from the fly 218 and the rear pressure-sensor was positioned about2.13 meters (about seven feet) from the front pressure-sensor 212. Thepressure information captured by the pressure sensors was transmitted toa computer run software program for analysis and display.

FIG. 5B shows the configurations of air beams 14 that were tested in theblast tube 200 as test samples 216. All of the air beams 14 tested inthe blast tube 200 had a diameter of about 0.6 meters. Test sample 216Bincludes two individual air beams 14 with a fly 218, a fly 218 and a gap213 between the two air beams, this is a further example of the firstconfiguration. The fly 218 may be made of polyvinyl chloride, polyesteror a combination thereof. Test sample 216B¹ is the same as test sample216B except the fly 218 is made from an auxetic material, this isanother example of the first configuration. In certain configurationswhere there is no gap 213 between laterally adjacent air beams 14, thoselaterally adjacent air beams 14 are configured to be in an abuttingrelationship or position. Test sample 216C includes three individual airbeams 14 with a fly 218 and no gap 213 between the air beams 14. Testsample 216C is another example of the first configuration. Test sample216D includes three air beams 14A that are positioned adjacent the fly218 to form the first layer 10A and three air beams 14B that form thesecond layer 10B. The three air beams 14B are adjacent to and alignedcentrally with the air beams 14A of the first layer 10A. Test sample216E includes the first layer 10A of three air beams 14A, the secondlayer 10B of three air beams 14B and the intermediate layer 10C of threeair beams 14C. All of the air beams 14 in test sample 216E are alignedcentrally with adjacent air beams 14.

FIG. 6 through FIG. 13 show examples of overpressure data that wascaptured in the blast tube 200. FIG. 6 shows three lines of captureddata from: the upstream pressure sensor 210, shown as line 210A; thefront pressure sensor 212, shown as line 212A and the rear pressuresensor 214, shown as line 214A when there is no target sample present,which may be referred to herein as a reference shot. The reference shotallowed an examination of the characteristics of the blast pulse, andhow the blast-pulse profile changes as the blast wave transits thelength of the blast tube 200. Without a specimen in the test section,the incident pulse is undisturbed by target reflections.

Table 4 shows the characteristics of the reference shot.

TABLE 4 A summary of the reference shot characteristics. MeasurementLocation P_(SO) (Peak), psig Upstream pressure sensor 6.81 Frontpressure sensor 6.59 Rear pressure sensor 5.91

FIG. 7 shows the overpressure-data captured when the target sample 216B(first configuration with the gap 213) was present. Line 212B shows thepressure data captured from the front pressure sensor 212 and line 214Bshows the pressure data captured from the rear pressure sensor 214. Theline 214B shows and incident-peak pressure that represents the maximumvalue of blast overpressure (psig) associated with the initial shockwave caused by the explosive event 204. Subsequent pressure peaks areshown in line 214B that have higher values, but these are associatedwith reflections that occur when the blast wave encounters the targetsample 216 (shown as reflection peaks in FIG. 7). While these pressurevalues are real and do act on the test sample, a more accurateassessment of the reduction of transmitted blast overpressure requiresthat the pressure wave transmitted through the structure be compared tothe peak that would exist if the structure were not present. Therefore,in the present analysis the transmitted peak shown in line 214B wascompared to the incident-peak pressure shown in line 212B, and not thereflected peaks. In FIG. 7, the transmitted pressure shown in line 214Bwas about 30.7% lower than the incident-peak pressure shown in line212B. The transmitted pulse retained a shock front.

FIG. 8 shows the overpressure data captured when the target sample 216B¹(first configuration with the gap and an auxetic fly) was present in theblast tube 200. The transmitted pressure shown in line 214B¹ was about35.3% lower than the incident-peak pressure shown in line 212B¹. Thetransmitted pressure retained a shock front.

FIG. 9 shows the overpressure data captured when the target sample 216C(first configuration with no gap) was present in the blast tube 200. Thetransmitted pressure shown in line 214C¹ was about 67.2% lower than theincident-peak pressure shown in line 212C¹. The incident pressure inthis run was higher than for others (8.10 psig vs. approximately 6.0psig). The transmitted pulse appears to have a short, finite rise time,but still retained a shock-like characteristic.

FIG. 10 shows the overpressure data captured from a second explosiveevent (shot) when the target sample 216C (first configuration with nogap) was present in the blast tube 200. The transmitted pressure shownin line 214C² was about 46.8% lower than the incident-peak pressureshown in line 212C². The transmitted pulse retained a shock front.

FIG. 11 shows the overpressure data captured when the target sample 216D(second configuration) was present in the blast tube 200. Thetransmitted pressure shown in line 214D¹ was about 78.5% lower than theincident-peak pressure shown in line 212D¹. The transmitted pulse didnot have an associated shock front; the shock is completely absent inthe transmitted pulse. The maximum transmitted pressure also did notoccur in the first peak of the transmitted wave.

FIG. 12 shows the overpressure data captured when a second explosiveevent 204 occurred (second shot) and the target sample 216D (secondconfiguration) was present in the blast tube 200. The transmittedpressure shown in line 214D was about 76.9% lower than the incident-peakpressure shown in line 212D. The transmitted pulse did not have anassociated shock front. It was determined that the pressure spikes shownin line 212D at about t=11.0 milliseconds (indicated with * in FIG. 12)are anomalies and can be disregarded.

FIG. 13 shows the overpressure data captured when the target sample 216Ewas present in the blast tube 200. The transmitted pressure shown inline 214E was about 79.9% lower than the incident-peak pressure shown inline 212E. The transmitted pulse did not have an associated shock front.

FIG. 14 shows a comparison of the peak-incident pressure data andtransmitted overpressure data captured when the various target samples216 were present within the blast tube 200.

The first configuration 216B with the gap 213 between laterally adjacentair beams 14 reduces the overpressure transmitted through the targetsample 216 by about 30-35%. This finding is highly representative ofblast resistance at full structural scale. Approximately the same degreeof overpressure reduction was detected in all of the applicant'sprevious free-field blast studies on single-layer inflated structureswith a gap between laterally adjacent inflated air beams.

Without being bound by any particular theory, if the inflation pressureand tube diameter are kept constant, when the structure 10 has no gapbetween adjacent air beams, the structure 10 is stiffer and capable ofcarrying a greater load than a structure 10 with a gap. When thestructure 10 has at least two layers 10A, 10B of air beams 14 with anequivalent tube-diameter and inflation pressure, the structure 10 willbe stiffer and stronger than a structure 10 with only one layer of airbeams 14. Furthermore, the configurations of air beams 14 that had atleast two layers 10A, 10B fully defeated the transmission of a shockwave.

1. A structure comprising at least a first layer of a plurality of airbeams and a second layer of a second plurality of air beams, wherein thesecond layer is positioned adjacent to and interior to the first layerfor defining an interior space of the structure.
 2. The structure ofclaim 1, wherein at least some of the plurality of air beams in thefirst layer are configured to be laterally abutting.
 3. The structure ofclaim 1, wherein at least some of the plurality of air beams in thesecond layer are configured to be laterally abutting.
 4. The structureof claim 2, wherein at least some of the plurality of air beams in thesecond layer are configured to be laterally abutting.
 5. The structureof claim 1, wherein the plurality of air beams in the first layer arealigned centrally with the plurality of air beams in the second layer.6. The structure of claim 1, wherein the plurality of air beams in thefirst layer are aligned offset with the plurality of air beams in thesecond layer.
 7. The structure of claim 1, wherein a span of theinterior space is about 200 meters.
 8. The structure of claim 1, whereina span of the interior space is selected from a group of about 175meters, about 150 meters, about 125 meters, about 100 meters or less. 9.The structure of claim 1, wherein the interior space has a peak heightof between about 2 meters and about 100 meters.
 10. The structure ofclaim 1, further comprising a connection system, wherein the connectionsystem comprises a shear control system for controlling or reducingshear between the plurality of air beams in the first layer and theplurality of air beams in the second layer.
 11. The structure of claim10, wherein the shear control system comprises at least one set of astrap and a pocket, wherein the pocket is secured to an outer surface ofan air beam in one of the first layer or the second layer and the strapis wrapped around the air beam in one of the first layer or the secondlayer and an air beam in the other layer.
 12. The structure of claim 10,wherein the shear control system comprises a set a first hug strap, asecond hug strap and a length of webbing, wherein the first hug strap issecurable about an outer surface of an air beam in the first layer orthe second layer and the second hug strap is securable about an outersurface of an air beam in the other layer, wherein the first hug strapis offset from the second hug strap and both hug straps are configuredto receive a portion of the length of webbing therethrough within acontact area between the first layer and the second layer.
 13. Thestructure of claim 10, wherein the shear control system comprises a setof a pair of fixed point connectors and a bracing strap, wherein one ofthe pair of fixed point connectors is secured to an outer surface of anair beam in the first layer or the second layer and another of the pairof fixed point connectors is secured to an outer surface of an air beamin the other layer, and wherein the bracing strap is connected at eachend to one of the pair of fixed point connectors.
 14. The structure ofclaim 13, wherein the bracing strap has an adjustable length.
 15. Thestructure of claim 10, wherein the shear control system comprises a hookportion and a loop portion, wherein the hook portion is secured to anouter surface of an air beam in the first layer or the second layer andthe loop portion is secured to an outer surface of an air beam in theother layer, wherein the hook portion and the loop portion are mateableto form a hook and loop fastener.
 16. The structure of claim 1, furthercomprising a third layer of a plurality of air beams, wherein the thirdlayer is adjacent the first layer.
 17. A structure that comprises atleast one layer of air beams that define an interior space of thestructure wherein laterally adjacent air beams are configured tolaterally abut each other.
 18. The structure of claim 17, wherein thereis one layer of air beams.
 19. The structure of claim 17, wherein thereis more than one layer of air beams, wherein an interior layer of airbeams defines the interior space.